repairing overheated merc 150 xr2

[KevinW]

My 1987 Mercury 150XR2 recently overheated, reasons yet unknown, possibly picked up bag or similar debris from river, blocking flow. I changed the impeller and both thermostats and also did a compression check. Although the engine was cold during test, all cylinders tested at 115 on gauge. I also retourqued all of the head bolts per manual specs.<br />Problem is, engine bogs and dies going from idle to "plane speed". It seems to be rich, as there are carbon deposits on plugs and piston tops. Ironically, pushing the enrichening valve on the key switch keeps the motor running. There is plenty of top end power. It runs very smooth at 30 MPH and has the guts to go up to 50 MPH really quickly. Hole shots are terrible becuase of bogging. Fresh fuel was put in at the begining of the season.<br /><br />Any sugesstions of possible parts melted from overheat? Can I supply any more info?

 

[12Footer]

Re: repairing overheated merc 150 xr2

Give it a good fogging. The deposits reveal carbon,and this goo probably is baked-onto the reeds too (from the heat).<br />Also check the internal fuel filter at the pump. Just thinkin alloud as usual.<br />Good luck with it.<br />Check the compression tube to the block from<br />the fuel pump too,as it has a tendancy too melt durring melt-downs...Good thing you caught it in time tho

<br /><br /><br />------------------<br />Water,water everwhere...And all I can catch is CATFISH!!!

 

[MERCMAN]

Re: repairing overheated merc 150 xr2

If you can hit the enrichment and it comes on out of the hole it is lean. I would perform a cylinder leak down test because it sounds to me you have cylinder damange on all or a few cylinders. I've found that a compression test can show good but when leak down test is done you find that there is damange below the rings and if that occurs then there will be a lean condition that's why when you hit the enrichment it runs better. Hope this is not your case but it can happen Good luck

 

[ODDD1]

Re: repairing overheated merc 150 xr2

Mercman is right about the lean/ poss skirt scoring...heat damage like that makes the motor 'want' more fuel, so it acts lean..you are gonna have carbon in the motor, your mixing oil in with the gas! if you get past the scoring, definately look at the bleed system lines and specially the check valves..they were a prob on the XR2's